21780330 has 64 divisors (see below), whose sum is σ = 61423488. Its totient is φ = 4872960.

The previous prime is 21780329. The next prime is 21780337. The reversal of 21780330 is 3308712.

It is a self number, because there is not a number n which added to its sum of digits gives 21780330.

It is not an unprimeable number, because it can be changed into a prime (21780337) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1752 + ... + 6828.

It is an arithmetic number, because the mean of its divisors is an integer number (959742).

Almost surely, 2^21780330 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21780330, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30711744).

21780330 is an abundant number, since it is smaller than the sum of its proper divisors (39643158).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21780330 is a wasteful number, since it uses less digits than its factorization.

21780330 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5111.

The product of its (nonzero) digits is 1008, while the sum is 24.

The square root of 21780330 is about 4666.9401110364. The cubic root of 21780330 is about 279.2681995968.

The spelling of 21780330 in words is "twenty-one million, seven hundred eighty thousand, three hundred thirty".